Electromagnetically energized impact forming device

ABSTRACT

AN ELECTROMAGNETICALLY ENERGIZED IMPACT FORMING DEVICE WHEREIN A SOLID PROJECTILE IS DRIVEN AT HIGH VELOCITY AGAINST A WORKPIECE SUFFICIENT TO COLD WORK OR FORGE THE WORKPIECE INTO A PRESELECTED ON FIGURATION. THE PROJECTILE IS MOVABLE WITHIN A CONFINING BARREL OR TUBE, ONE END OF WHICH IS LOCATED AT THE STATION WHERE THE WORKPIECE IS PLACED. THE WORKPIECE MAY BE DISPOSED ON AND/OR WITHIN ANY SUITABLE WORK SURFACE SUCH AS A FORMING DIE IN SUCH POSITION TO INTERCEPT THE PROJECTILE MOVING THROUGH THE BARREL OR TUBE. A PLURALITY OF COILS SURROUND THE BARREL AND ARE ELECTICALLY ENERGIZED OR PULSED IN SUCH MANNER AS TO GENERATE MAGNETIC FIELDS LONGITUDINALLY SPACED ALONG THE LENGTH OF THE BARREL AND WHICH ARE EFFECTIVE TO PROPEL THE PROJECTILE TOWARD AND INTO ENGAGEMENT WITH THE WORKPIECE. THE COILS MAY BE REVERSIBLY ENERGIZED AT THE COMPLETION OF THE WORK STROKE OF THE PROJECTILE TO MOVE AND RETAIN THE PROJECTILE IN A RAISED POSITION TO AWAIT THE NEXT SUCCEDING CYCLE.

Oct. 12, 1971 Filed June 20, 1968 E. MITTELMANN ELECTROMAGNETICALLY ENERGIZED IMPACT FORMING DEVICE 3 hay@ /3/ I5 Sheets-Sheet 1 fUGEA/f' N/rrfz MHA/N www E. MITTELMANN 3,611,783

ELECTROMAGNETICALLY ENERGIZED IMPACT FORMING DEVICE oct. 12,4 1971 3 Sheets-Sheet 2 Filed June 20, 1968 iin- Oct. 12, 1971 E` MITTELMANN 3,611,733

ELECTROMAGNETICALLY ENERGIZED IMPACT FOHMING DEVICE Filed June 20, 1968 3 Sheetsheet 3 Q MIWNI Allilnm! W w3@ 3,611,783 Patented Oct. 12, 1971 U.S. Cl. 72-430 5 Claims ABSTRACT F THE DISCLSURE An electromagnetically energized impact forming device wherein a solid projectile is driven at a high velocity against a workpiece sufficient to cold work or forge the workpiece into a preselected coniiguration. The projectile is movable within a confining barrel or tube., one end of which is located at the station where the workpiece is placed. The workpiece may be disposed on and/or within any suitable work surface such as a forming die in such position to intercept the projectile moving through the barrel or tube. A plurality of coils surround the barrel and are electrically energized or pulsed in such manner as to generate magnetic fields longitudinally spaced along the length of the barrel and which are effective to propel the projectile toward and into engagement with the workpiece. The coils may be reversibly energized at the completion of the work stroke of the projectile to move and retain the projectile in a raised position to await the next succeeding cycle.

Heretofore, various attempts have been made to accelerate a ferro-magnetic mass by means of electromagnetic energy whereby the energy of a magnetic iield is utilized to supply the accelerating force. rlfhese previous attempts have been directed previously to imparting acceleration to a single ferro-magnetic mass such as a ballistic projectile by energizing a coil or the like for a single time period so that the magnetic iield generated thereby acts in a single pulse or a single time period only on the projectile to accelerate its motion. This process has been considered as a single shot event. Generally, the acceleration to the ferro-magnetic mass has been imparted by a suitably designed coil surrounding a tubular structure into which the ferro-magnetic mass is confined. By applying a single current pulse to the coil, usually by discharging a capacitor into the coil, a magnetic iield is generated surrounding the tubular structure which iield is directional longitudinally of said structure so as to impart movement to the projectile.

The limitations of such a system have become obvious to those skilled in the art inasmuch as with the current pulse obtained by means of discharging a capacitor into a coil, the available energy for generating the iield is limited by the size of the capacitor and the voltage applied to it. Furthermore, in order to avoid the necessity of very high capacity current sources, it becomes necessary to charge the capacitor through a current limiting resistor or the like, thus introducing a relatively large time constant which prevents energizing the accelerating coil in sufficiently short intervals of time which is required in order to accelerate the projectile.

IIt is therefore a primary object of the present invention to provide a novel method and means for practicing the said method t0 provide for the acceleration to high nal velocities of a ferro-magnetic mass by means of a plurality of accelerating coils suitably distributed along the path which the mass Will travel and applying energy sequentially to the individual coils in proper intervals of tlme effective to generate an electromagnetic field which 1s advanced rapidly along said path.

A further object of the invention is to provide for the acceleration of the ferro-magnetic mass by means of controlled solid state devices, such as silicone controlled rectiiiers or the like, using suitable commutating and timing circuits to control the initiation and termination of energy pulses in the individual coils effective to generate an electromagnetic eld that rapidly advances along the path which the mass will travel.

Another object of the invention is to provide means to control the triggering of the current impulses at intervals determined by the velocity of the travelling ferromagnetic mass as a function of the velocity obtained by the acceleration imparted to it by preceding coils through which the mass has already travelled.

An additional object of the invention is to provide means permitting the triggering of the first accelerating coil from a reference level of position and relative velocity and to provide means to measure and control the :[inal velocity obtained by the mass.

lAnother object of the invention is to position the indivldual coils at such geometric intervals along the path of travel for the mass so as to permit maximum acceleration of sald mass with a minimum geometric length of guidmg structure for the mass which directs the movement of the ferro-magnetic mass in its straight line path.

A still further object, having once obtained the desired acceleration to the ferro-magnetic mass, is to apply the lkinetic energy imparted to it to forming metallic or similar parts as, for example, in forging operations. In connection with the above cited objectives, means are also incorporated herein which permit the return of the accelerated mass from its point of impact with a workpiece to its original position of reference, thus making it possible to repeat the cycle at proper intervals of time.

Additional objects and advantages of the present invention will be apparent to one skilled in the art upon reference to the following disclosure and to the accompanying drawings forming a part of said disclosure, and wherein:

ZFIG. l is a schematic diagram showing the mechanical and electrical components which comprise a preferred embodiment;

FIGS. 2A and 2B are electrical wiring diagrams showing a preferred form of control and firing circuit for use in the electromagnetic impact device of the present invention.

Referring now to FIG. l of the drawing, the numeral 1 denotes an elongate guiding tube in which a ferro-magnetic mass 2 is permitted to move freely in `a vertical direction. Initially, as will be hereinafter more fully eX- plained, the mass 2 is held in a raised position at the top of the tube by means of a holding magnet coil 3 energized from a source 4 of direct current energy in series with a normally closed switch 5 which is shown in its open position. Below the holding magnet 3 there are disposed a plurality of accelerating coils, for instance, as shown at 6, 7 and 8. Once switch 5 is interrupted, the ferro-magnetic mass 2 may fall freely downward being guided by tube 1. Tube 1 is provided with openings or ports 9, 10, 11, 12 and 13 spaced therealong in such a manner that appropriate photo-electric means such as indicated respectively at 9a, 10a, 11a, 12a and 13a, and further at 9b, 10b, 11b, 12b and 13b, can be disposed adjacent to said ports, light emitting means 9a, 10a, 11a, 12a and 1361,

emitting a light beam therethrough and focusing on photo sens1t1ve means 9b, 10b, 11b, 12b and 13b, thus permitting the falling mass 2 to interrupt the optical circuit of said photo-electric means. This light interruption will, in a manner to be described below, initiate an accelerating impulse which is applied to the ferro-magnetic mass 2 by means of the energy converted in the accelerating coils 6, 7 and 8 whereby the mass attains a resultant high velocity.

As the ferro-magnetic mass falls freely, it will first interrupt a light beam supplied from the source 9a of photoelectric device 9b and its associated circuitry. Electrically connected to this photo-electric device 9b is an adjustable time delay circuit 16 which provides an output signal in response to the impulse received by the photocell device 9b caused by the interruption of its light beam by mass 2. The output signal of the time delay circuit 16 is, in turn, applied as an input signal to a triggering circuit 17 which includes a silicon controlled rectifier circuit connected in series with the accelerating coil 6 and the aforesaid source 4.

Similar arrangements are provided in connection with accelerating coils 7 and 8 and their associated photocell devices a and 11a, the time delay circuitry being represented at 18 and 20 and the associated rectifier circuitry therefor at 19 and 21, respectively.

A suitable anvil 26 is disposed at the lower end of the vertical tube 1 and receives the workpiece 27 to be formed or forged by the mass 2.

-If desired, the tube 1 may be provided with the additional pairs of ports as identied at 12 and 13 which are disposed at a known distance apart. Suitable light sources 12a and 13a respectively function to provide a light beam to each of said ports, focusing said beams on photocell means 12b and 13b respectively.

As seen, ports 12 and 13 are located adjacent the lower end of the tube 1 and their purpose is to enable the impact velocity of the mass 2 t0 be measured immediately before the mass 2 strikes the workpiece 27.

This is accomplished by utilizing the output pulse from photo-electric device 12b to provide a starting pulse for a conventional digital counter 25, and an output pulse from the photo-electric device 13b as a stop pulse for said counter 25. By knowing the distance X between ports 12 and 13, the time it takes for the mass 2 to travel said distance can be readily determined.

Reference numerals 28 and 29 designate additional photo-cell light sources and photocells connected to their associated trigger circuits which operate with ports 30 iand 31 formed in the tube or barrel 1. Numeral 32 identies a time delay circuit which provides a cut-off signal for photocell device 29 for a predetermined period of time which is longer than the time required for the accelerated mass 2 to travel between port 13 and the final impact point when it strikes the workpiece 27. Reference numeral 33 identifies an accelerating coil placed between ports 13 and 30 and is intended to be energized when the travelling mass 2 rebounces after impact with the workpiece 27 and triggers the photocell devices 28 and 29 which, in turn, by means of pulse duration timing circuit 34 and an associated silicon controlled rectifier unit 35 provides a predetermined pulse of current to accelerating coil 33 to effect the return of the projectile to its initial position at the top of tube 1 whereat it is held in suspension by the holding coil 3.

The operation of the system consisting of the elements as have been schematically identified in FIG. 1 is as follows.

With the ferro-magnetic mass 2 placed and suspended in position in the center of the energized holding coil 3, the workpiece 27 to be formed is placed into position in anvil 26. This placement may be accomplished either manually or by any suitable automatic means well known to those skilled in the art. The forging operation is thus initiated by opening switch 5 to release the ferro-magnetic mass 2 whereby it begins to fall freely by reason of gravity. In its free fall, the mass 2 interrupts the light beam emanating from source 9a so that an output voltage is applied to the time delay circuit 16 which, in turn, provides a triggering pulse to the trigger circuit 17. The latter is then operative to energize the silicon controlled rectifier circuit of unit 17 at approximately the instant of time that is required for the ferro-magnetic mass 2 to reach the domain of influence of the flux of accelerating coil 6. This instant of time depends upon the characteristics, mechanical and electrical, of the particular system in use as will be hereinafter more fully explained.

In actual practice, it has been determined that maximum acceleration of the mass or projectile 2 will be obtained if the pulse duration is such that the leading edge of the ferro-magnetic mass reaches the center position of the coil 6 before the end of the pulse duration. Or more precisely, the pulse duration `must be shorter than the time required for the accelerated mass to reach the center position of the coil. The relationship between pulse duration and accelerating current is an inversely proportional one inasmuch as the energy required for the accelerated mass to reach the center position of the coil is expressed in ampere-seconds and, consequently, one has the choice to apply low currents for relatively long time periods to obtain the same acceleration or high currents for relatively short time periods. It is one of the main features of the present invention that very high currents in the order of magnitude of several thousand amperes are preferred to be utilized for time durations in the order of magnitude of milliseconds. Only in this manner does it become possible to apply several accelerating pulses and obtain high final velocities for the projectile 2. Low current levels with associated long acceleration time periods require an extremely long guide tube which would make the system impractical particularly in industrial use.

With the coil 6 thus energized, the mass 2 is substantially accelerated thereby and propelled downwardly through barrel 1. As the mass 2 continues in its downward ight it next sequentially interrupts the light beam from sources 10a and 11a whereby the trigger circuits 19 and 21 associated with accelerating coils 7 and 8 respectively are actuated to energize said coils 7 and 8 whereby to further accelerate said mass 2.

The mass 2 is thus propelled at a substantially high velocity and into engagement with the workpiece 27 to thereby forge the same into the configuration as determined by anvil 26.

In actual practice a mass weighing approximately 22 grams has attained a striking or final velocity of approximately 241 feet per second using peak current levels of about 9000 amperes to energize the accelerating coils 6, 7 and 8.

Projectiles weighing upwardly of six pounds and a final velocity in the neighborhood of 400 feet per second can be obtained with the present electromagnetic machine assembly and the technique of the operation of its electrical control circuitry as will now be more fully explained.

With reference now directed to FIGS. 2A and 2B, the control circuitry for the electromagnetic impact machine of the present invention includes the previously identified power source 4 which may be any conventional configuration such as the solid-state three-phase full wave rectifier unit herein shown. The rectifier unit is connected to a suitable alternating current source such as a three-phase, 440 volt source.

The rectified output of the rectifier unit 4 is taken across conductors 40, 41, the latter being system ground.

The aforementioned holding coil 3 and switch 5 are seen to be connected in arcs with each other and across conductors 40, 41 so that when said switch 5 is closed, coil 3 is energized.

As also aforementioned, when switch 5 is opened coil 3 is deenergized and the mass or projectile 2 in the tube 1 is permitted to free fall therethrough.

As said mass falls, its intercepts the light emanating from light source 9b, 9a in the time delay circuit 16.

The photocell device 9b is connected across the base circuit of a unijunction transistor Q1.

Unijunction transistor Q1, in conjunction with a potential dividing circuit, consisting of resistance R1 and photocell device 9b, are the essential elements governing the initiation of the triggering pulse. Unijunction transistors, as well known, have the characteristic behavior of falling into conduction as soon, but not before, the voltage applied between its No. 1 base and emitter (or gate) exceeds a certain fraction of the voltage applied between bases 1 and 2. Conduction takes place in all cases as soon as this fractional value of the base 1 to base 2 voltage is exceeded. The photocell device 9b will represent, as long as light irnpinges upon it, a certain, relatively low value of resistance. The value of R1 is so selected or so adjusted that the ratio of the voltage appearing across the photocell device 9b and that of the total voltage supply is less than the ratio required to trigger the unijunction transistor into conduction. As soon as the travelling ferro-magnetic mass in the tube passes by and covers the opening 9 the light beam passing therethrough is interrupted. The resistance of the photocell changes from its initial low value to a high value determined by its dark resistance and, simultaneously, the potential across it will rise to a level corresponding to a ratio of emitter to base 2 voltage which exceeds the triggering level. The steepness of the resistance change is determined by the dimensions of the opening 9 in the wall of tube 1 and the velocity of the travelling ferro-magnetic mass 2. This time may vary from a few milliseconds to values as low as microseconds. It is, therefore, required to choose a unijunction transistor that is capable of responding up to high frequency pulses. Associated with photocell 9b and unijunction transistor Q1 is a low current type of silicone controlled rectifier 43 which is connected across conductors 48 and 49 as to be supplied by a direct current voltage corresponding to the charge deposited on a capacitor identified at C1 in parallel with SCR 43 and a load resistance R5 connected in the cathode circuit of said transistor. As soon as transistor Q1 is triggered into conduction, a pulse is applied to the gate of SCR 43 by means of the secondary S1 of a pulse transformer T1 having its primary P1 connected into the gate circuit of said SCR 43. The duration of the pulse output produced by SCR 43 and appearing across resistance R5 is determined by the time constant of the product of resistance R5 and capacitance C1.

The output of SCR 43 (terminals A, B) is connected to the input of an electronic switch consisting essentially of a pair of commutating silicone controlled rectifiers (SCR) 50, 51 connected in parallel across conductors 58, 59 to a direct current source of energy as identified at 60 in FIG. 2B. A commutating capacitor C2 and a charging resistor R6 are connected into the anode circuit of SCR 50, 51 respectively.

The photocell circuit as described before delivers a triggering pulse to terminal A and the gate electrode of SCR 50. SCR 50 is thereby fired to in turn apply a pulse output signal to terminal 62 of oscillator circuit 63. The voltage appearing across resistor R7 of said circuit stabilized by capacitor C4 supplies energy to a Zener diode Z1, to thereby provide a constant voltage source to the input of a relaxation oscillator of the unijunction type consisting of unijunction transistor Q2 and associated circuitry. The pulse output signal from oscillator Q2 is seen to connect to the gate electrode of SCR 65 of triggering circuit 17 which is also connected across conductors 58, 59. The anode of SCR 65 is connected by conductor 68 to the gate electrode of SCR 71 which is connected in series with the first accelerating coil 6. The frequency of oscillations and thereby the time delay between the firing of SCR 50 and the triggering of SCR 65 is determined by the value of the variable resistance R2 in series with capacitor C5, the emitter of the unijunction transistor Q2 being connected to the junction point of R5 and C5. At the end of the first full cycle of oscillation of transistor Q2, SCR 65 is triggered to deliver a pulse to the gate electrode of (SCR) 71. At the same time, the secondary 74 of the pulse transformer 75 connected with the base circuit of unijunction transistor Q2 is energized to deliver a pulse to the gate electrode of the commutating SCR 51 of the electronic switch through conductors 76, 77 effective to turn off said SCR 51 and thereby removing the firing voltage from the unijunction oscillator circuit, thus disabling the oscillator Q2. During the interval when SCR 65 is fired into conduction by the unijunction oscillator Q2, it is prevented from retiring by the simple expediency of discharging a capacitor C6 through said SCR, the charging resistor R9, together with capacitor C6, having a relatively long time constant in the order of magnitude of seconds, which is sufficient to prevent operation of the triggering SCR 65 before the next projectile 2 is placed by the operator into the guiding tube 1.

The pulse duration, i.e., the time during which SCR 71 is permitted to conduct to effect the acceleration of the mass 2 in the first accelerator stage is determined by the frequency of the timing circuit indicated in FIG. 2A by the circuit identified at 85. This circuit is essentially similar to the time delay circuit 16 with the only difference being that the high speed electronic switch circuit thereof is triggered at the gate electrode of SCR 87 from a pulse obtained from the 'secondary S2 of the pulse transformer T2 connected into the output circuit of the unijunction oscillator Q2 of said time delay circuit 116. The purpose of timing circuit is to terminate the conduction period of SCR 71. This is accomplished by applying a triggering pulse to the gate of SCR 88 after a predetermined interval of time.

SCR 88 as seen in FIG. 2A, is connected in triggering control relation with SCR 71, and has its gate electrode connected by conductor 90 to the output (cathode of SCR 92) of timing circuit 85.

When the oscillator Q2 turns on its output pulse signal is taken from the secondary S2 of transformer T2 and is applied by conductors 91, 92 across the gate-cathode circuit of SCR 187 effective to turn on said SCR. As a result, the unijunction Q5 of timing circuit '85 is made to conduct to provide a pulse output suiiicient to turn on SCR 92, which, in turn, brings SCR l88 into conduction. When SCR 88 conducts it enables capacitor C9 connected across SCR 88 and 71 to discharge through SCR 88 to thereby force SCR 71 to turn olf and discontinue the energization of coil 6.

SCR 88 is fired at a time established by the in-circuit value of the variable resistance R10 in the frequency determining circuit of unijunction transistor Q3.

The mass 2 is thereby accelerated as it travels downward through tube 1.

When the mass 2 passes the next successive port 10 formed in tube 1 it interrupts the light emanating from photocell device 10a and is operable to initiate another similar energizing cycle, this time being effective to actuate circuit 18 which is identical in operation to time delay circuit 16. It is considered therefore unnecessary to additionally describe the circuit structure of time delay circuit 18; however, with reference to FIG. 2B it will be noted that the transformer T3 connected into the input to the switching SCRs 50, 51 of said circuit 18 is provided with two secondary windings S1 and S2.

Secondary winding S1 connects to the cathode-gate circuit of SCR 50 and is effective to transfer the pulse output from transistor generator Q1 of said circuit 18 to said SCR 50 and canse the same to turn on. As in the previous time delay circuit 16, the output of the switching SCRs 50, 51 at terminal 62 is applied to the frequency determining network of relation oscillator circuit 63` whereby to cause said oscillator Q2 to fire.

In time delay circuit 18, the output signal from oscillator Q2 is applied directly through conductor 96 to the commutating SCR of the firing circuit 19 for coil 7 rwhich 7 SCR is comparable to SCR 88 of the firing circuit 17 for coil 6, and which is effective to terminate the energization of coil 7.

The output signal of generator Q1 that is impressed upon secondary Winding S2 of transformer T3 in circuit 1'8 is applied directly through conductor 99 to the trigger SCR 98 of firing circuit 19 for coil 7.

The output signal thus generated from firing SCR 98 is applied through conductor 101 to the switching SCR for coil 7 comparable to SCR 71 for coil 6 which is thereby effective to initiate the energization of coil 7.

The time interval between energizing coil 7 and deenergizing said coil is determined by the frequency network of generator Q2 on the time delay circuit 18 which network is identical to network 63 in the time delay circuit 16 of FIG. 2A.

As a result, coil 7 is energized at approximately the instant mass 2 arrives at the center of said coil whereby it is again electromagnetically accelerated to a higher velocity level.

The mass 2 continues its downward flight in tube 1 and next passes port 11 whereupon it actuates photocell device 11a which, in turn, causes the operation of time delay circuit 20 and firing circuit `21 and the resultant energization of coil 8. Hence, the mass 2, as it passes through coil 8, is similarly accelerated to a substantially high velocity sufficient to cold forge the workpiece 27 within the anvil 26.

While the device described herein utilizes three stages of coil acceleration it is to be understood that additional stages may be incorporated into the same to thereby result in obtaining higher levels of velocity for the ma'ss 2.

In actual practice, a forging device built according to the present invention has utilized high power silicone controlled rectifiers of the type 280 to accelerate a mass of 22 grams to a final impact velocity of 241 feet per second. This acceleration was accomplished in three stages, each stage including an accelerating coil having approximately 20 turns and each of the coils being energized with current pulses of 10,000 amperes lasting for a few milliseconds.

The final accelenation and therefore the final velocity is a direct function of the ampere turn seconds. In the particular case of the 22 gram mass the total energy required to obtain the final velocity of 241 feet per second is approximately 600 ampere turn seconds. In the particular case of the 22 grams mass the total energy required to obtain the final velocity of 241 feet per second is approximately 600 ampere turn seconds. To obtain higher velocities in the same structure or, for that matter, in a similar structure of correspondingly different length dimensions for tube 1, the ampere turn seconds should be raised proportionally to obtain the required final velocity. Therefore, the final velocity of 480 feet per second and using a 22 gram mass would require 1200 ampere-turn-seconds. Similarly, to accelerate a projectile having twice the mass, or 44 grams, to the same velocity of 241 feet per second also requires 1200 ampere-turn-'seconds.

The required number of ampere-turn-seconds can be obtained either by increasing the number of individual accelerating stages, each one having its own accelerating coil, or by increasing the amount of current in each stage in order to obtain a higher level of ampere-turns.

The duration of the current pulse in each coil 6, 7, 8 is also limited by the dimensions of the coil. The increase of the ampere-turns will result in higher accelerations only if these ampere-turns are referred to the same unit length, i.e., the ampere-turns per inch or ampere-turns per centimeter are increased proportionally to the required velocities. This fact precludes the changing of the length dimension of the coil in the axial direction and necessitates the use of increased current. The increase in current can be obtained either by the use of properly rated high power silicone controleld rectifiers capable of dissipating the necessary current, or if such devices are not available, by the use of several silicone controlled rectifiers in a parallel combination, energizing jointly and simultaneously the same accelerating coil. `Circuits making possible the parallel operation of high power silicone controlled rectifier devices in a pulse type operation are well known to those skilled in the art of silicone controlled rectifier techniques.

Accordingly, the present invention is not limited to the example shown, the obtainable accelerations are limited only by the availability of suitable components capable of providing the necessary current levels.

The current level which can be supplied in any single accelerating stage is limited by two factors, namely, the heat dissipation in the silicone controlled rectifier units energizing the coil and the heat dissipation in and voltage drop across the accelerator coils themselves. The limitations of heat dissipation in the silicone controlled rectiers can be overcome as pointed out before, either by the use of properly higher rated controlled rectifier units, or by the parallel combination of several such units. The limitations, due to voltage drop across the accelerator coil with its associated heat dissipation, can be overcome according to the invention by the proper choice of materials. For instance, using high conductivity silver or super conducting materials in lieu of the customary copper in the fabrication of the accelerating coils. Accordingly, the acceleration of ferro-magnetic masses, by means of discrete current pulses according to the invention, is not limited to any particular mass or any particular velocity li'rnit.

As previously mentioned, and as is diagrammatically illustrated in FIG. l, additional ports 12 and 13 are located adjacent the lower end of the tube 1 and their purpose is to initiate circuitry effective to enable the impact velocity of the mass 1 to be measured immediately before the mass 2 strikes the workpiece 27.

This is accomplished by utilizing the output pulse from photo-electric device 12a which is similar to photocell device V9a to provide a starting pulse for a conventional digital counter 25, and an output pulse from the photoelectric device 12a as a stop pulse for said counter 25. By knowing the distance X between ports '12 and 13, the time it takes for the mass 2 to travel said distance can be readily determined, photocell device 12 being first actuated to start the counter 25 and photocell device 13a being subsequently actuated to stop said counter.

`Reference numerals 28 and 29 also designate additional photocell light sources and photocells similar to photocell devices 9b, y10b and 11b which are connected to their associated trigger circuit 34 which is similar to circuit 16 heretofore described operate with ports 30 and 31 formed in the tube or barrel 1. Numeral 32 identifies a time delay circuit of any conventional circuitry which provides a cutoff signal for photocell device 29 for a predetermined period of time which is longer than the time required for the accelerated mass 2 to travel between port 13 and the final impact point when it strikes the workpiece 27. Reference numeral 33 identifies an accelerating coil placed between ports 31 and 30 and is intended to be energized when the travelling mass 2 rebounces after impact with the workpiece 27 and triggers the photocell devices 28 and 29 which, in turn, by means of pulse duration timing circuit 34 and an associated silicon controlled rectifier unit 35 similar to unit 17 provides a predetermined pulse of current to accelerating coil 33 to effect the return of the projectile to its initial position at the top of tube 1 whereat it is held in suspension by the holding coil 3 to await the next impact cycle.

It is also contemplated that the operator of the instant impact machine may desire to manually place the mass 2 at the top end of the tube 1 after each forging cycle of operation. In such assembly, the coil 33 and its associated control circuitry are not required.

The following table sets forth the identification and magnitude of the electrical components incorporated into the impact forming device.

Components: Specification C1 2 nf C2 5 ,uf

C3 C4 .O5 Lf `C5 1 ,if C6 2 pf C7 .05 nf C8 5 Lf C9 C10 1 nf C11 2 ,tf C12 5 ,if C13 2 ,uf C14 2 nf R3` R4 0-10 meg R5 20 ohms R6 100K R7 R8 50K R9 1 meg R10 15K R11 450 ohms lR12 18 ohms R13 R14 450 ohms R15 18 ohms Having thus described a preferred embodiment of electromag-netic impact forming device, it is realized that the same is susceptible to various modifications, changes and combinations of components without departing from the inventive concepts thereof as are defined in the claims.

What is claimed is:

1. An electromagnetic impact forming device for accelerating a ferro-magnetic mass comprising a perforated tubular guide to confine the mass in a straight-line path of travel, a first electromagnet surrounding said guide, first photo-electric means having a pulse output in position to be actuated by said mass in its travel through said guide, first time delay circuit means connected to said photo-electric means and said first electromagnet being operable to energize said first electromagnet when the mass is passing therethrough effective to accelerate the motion of said mass, second time delay circuit means being operable to de-energize said first electromagnet, a second electromagnet surrounding said guide and spaced therealong from said first electromagnet, second photo-electric means disposed along said guide being spaced from said first photo-electric means and having a pulse output, third time delay means connected to said second photo-electric means and said second electromagnet being operable to energize said second electromagnet and effect a further acceleration to said mass, and fourth time delay circuit means connected to said second electromagnet and operable to de-energize said latter mentioned electromagnet.

2. An electromagnetic impact forming device comprising means for holding a workpiece to be formed, an electromagnetically responsive tool movable along a path and into impact enegagement with said workpiece, means for generating electromagnetic impulses in spaced relation along said path including coil means substantially effectively surrounding the path and effective to accelerate the tool as it moves along said path, coil energizing means actuatable by said tool effective to cause the coil means to generate electromagnetic impulses and accelerate said tool, and time delay means in said coil energizing means operable to delay the energization of said coil means for a predetermined time period subsequent to the actuation of the coil energizing means.

3. An electromagnetic impact forming device as is defined in claim 2 and wherein the coil energizing means includes circuit means to effect the de-energization of the coil means.

4. An electromagnetic impact forming device as is defined in claim 2 and wherein the path is formed by guiding tube means.

5. An electromagnetic impact forming device as defined in claim 4 and wherein the tube means is disposed in approximately a vertical plane.

References Cited UNITED STATES PATENTS 2,083,168 6/1937 Larson 72-430 3,179,867 `4/ 1965 Delgado S10-13 3,225,228 12/1965 Roshala 310-12 3,435,312 3/1969 De Coster 310-14 FOREIGN PATENTS 848,780 9/1952 Germany 310-14 CHARLES W. LANHAM, Primary Examiner G. P. CROSBY, Assistant Examiner U.S. Cl, X.R. 3l0-l4 

